I already had my hot water wired behind a ripple control system, and I assume the smart meter should be smart enough to distinguish between standard and night rate. Flick arranged my smart meter install. I emailed Flick, I'll report back anything interesting I find.
It sounds dumb, but there's a very good chance you'll need to pay for a physical visit for someone to reprogram your meter in order to be metered separately for controlled night and uncontrolled usage (yes you would think network-connected smart meters could be updated remotely...). It may even require a bit of rewiring if you weren't originally wired to have water heating billed separately.